Such a manipulator- or robot-guided folding or hemming tool is known from practice. The compressive forces developing during hemming are measured with a load cell, which is arranged at the connection point between the hemming tool and the robot hand The measured load values are transmitted via cable to an external indicator, which the operator can hold in his hand, or put down at any desired site at the folding or hemming bed or elsewhere. The measured loads are indicated in numerals on a indicator. This detection technique has various drawbacks. It cannot be used optimally especially when setting up and programming a hemming robot.